Move fluentTheme from window to view

ios/FluentUI/Core/ControlHostingView.swift

@@ -78,24 +78,19 @@ open class ControlHostingView: UIView {
     }
 
     @objc private func themeDidChange(_ notification: Notification) {
+        guard let themeView = notification.object as? UIView, self.isDescendant(of: themeView) else {
+            return
+        }
         updateRootView()
     }
 
     private func updateRootView() {
         self.hostingController.rootView = tokenizedView
     }
 
-    private var currentFluentTheme: FluentTheme {
-        if let windowFluentTheme = self.window?.fluentTheme {
-            return windowFluentTheme
-        } else {
-            return FluentThemeKey.defaultValue
-        }
-    }
-
     private var tokenizedView: AnyView {
         return AnyView(controlView
-                        .fluentTheme(currentFluentTheme)
+                        .fluentTheme(fluentTheme)
                         .onAppear { [weak self] in
                             // We don't usually have a window at construction time, so fetch our
                             // custom theme during `onAppear`

ios/FluentUI/Core/Theme/FluentTheme.swift

@@ -57,15 +57,27 @@ public extension Notification.Name {
     static let didChangeTheme = Notification.Name("FluentUI.stylesheet.theme")
 }
 
-extension UIWindow: FluentThemeable {
+@objc extension UIView: FluentThemeable {
     private struct Keys {
         static var fluentTheme: String = "fluentTheme_key"
+        static var cachedFluentTheme: String = "cachedFluentTheme_key"
     }
 
-    /// The custom `FluentTheme` to apply to this window.
-    public override var fluentTheme: FluentTheme {
+    /// The custom `FluentTheme` to apply to this view.
+    public var fluentTheme: FluentTheme {
         get {
-            return objc_getAssociatedObject(self, &Keys.fluentTheme) as? FluentTheme ?? FluentThemeKey.defaultValue
+            var optionalView: UIView? = self
+            while let view = optionalView {
+                // If we successfully find a theme, return it.
+                if let theme = objc_getAssociatedObject(view, &Keys.fluentTheme) as? FluentTheme {
+                    return theme
+                } else {
+                    optionalView = view.superview
+                }
+            }
+
+            // No custom themes anywhere, so return the default theme
+            return FluentTheme.shared
         }
         set {
             objc_setAssociatedObject(self, &Keys.fluentTheme, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
@@ -74,13 +86,6 @@ extension UIWindow: FluentThemeable {
     }
 }
 
-@objc public extension UIView {
-    /// Returns the current view's window's `FluentTheme`, or the default `FluentTheme` if no window yet exists.
-    var fluentTheme: FluentTheme {
-        return self.window?.fluentTheme ?? FluentThemeKey.defaultValue
-    }
-}
-
 // MARK: - Environment
 
 public extension View {

ios/FluentUI/Other Cells/ActionsCell.swift

@@ -53,10 +53,10 @@ open class ActionsCell: UITableViewCell, TokenizedControlInternal {
     var tokenSetSink: AnyCancellable?
 
     @objc private func themeDidChange(_ notification: Notification) {
-        guard let window = window, window.isEqual(notification.object) else {
+        guard let themeView = notification.object as? UIView, self.isDescendant(of: themeView) else {
             return
         }
-        tokenSet.update(window.fluentTheme)
+        tokenSet.update(fluentTheme)
         updateAppearance()
     }
 

ios/FluentUI/Other Cells/ActivityIndicatorCell.swift

@@ -26,10 +26,10 @@ open class ActivityIndicatorCell: UITableViewCell, TokenizedControlInternal {
     var tokenSetSink: AnyCancellable?
 
     @objc private func themeDidChange(_ notification: Notification) {
-        guard let window = window, window.isEqual(notification.object) else {
+        guard let themeView = notification.object as? UIView, self.isDescendant(of: themeView) else {
             return
         }
-        tokenSet.update(window.fluentTheme)
+        tokenSet.update(fluentTheme)
         updateAppearance()
     }
 

ios/FluentUI/Other Cells/CenteredLabelCell.swift

@@ -17,10 +17,10 @@ open class CenteredLabelCell: UITableViewCell, TokenizedControlInternal {
     var tokenSetSink: AnyCancellable?
 
     @objc private func themeDidChange(_ notification: Notification) {
-        guard let window = window, window.isEqual(notification.object) else {
+        guard let themeView = notification.object as? UIView, self.isDescendant(of: themeView) else {
             return
         }
-        tokenSet.update(window.fluentTheme)
+        tokenSet.update(fluentTheme)
         updateAppearance()
     }
 

ios/FluentUI/Table View/TableViewCell.swift

@@ -197,10 +197,10 @@ open class TableViewCell: UITableViewCell, TokenizedControlInternal {
     var tokenSetSink: AnyCancellable?
 
     @objc func themeDidChange(_ notification: Notification) {
-        guard let window = window, window.isEqual(notification.object) else {
+        guard let themeView = notification.object as? UIView, self.isDescendant(of: themeView) else {
             return
         }
-        tokenSet.update(window.fluentTheme)
+        tokenSet.update(fluentTheme)
         updateAppearance()
     }